A PREGNANT teenager offering sex to strangers on Craigslist has been strangled and her boyfriend brutally decapitated allegedly by a man they met in a park.

Brooke Slocum, 18, was held captive for five days at the Michigan home of suspect Brady Oestrike, 31 before she was found strangled in the boot of his car.

She had arranged to meet Oestrike at Wyoming’s Gezon Park after contacting him through Craigslist.

Police believe her boyfriend Charles Oppenneer, who went to the park with Slocum, was also killed before being beheaded.

Boyfriend Charles Oppenneer. Photo: FacebookSource:Supplied

Brooke Slocum held captive. Photo: FacebookSource:Supplied

According to WOOD TV8, Slocum offered to have sex with Oestrike if he paid for it. Her boyfriend Charles Oppenneer, 25, was to be present when they met.

The couple’s flatmate, McKenzi Hallo, said Slocum, who was eight months pregnant at the time of her death, would use the site to meet people for sex.

“She said, you know, they would go and meet up and stuff and normally they would do stuff in the car. And Charlie would just either sit in the front seat and wait, or he joined,” Hallo said.

According to his Facebook profile Brady Oestrike worked as a lineman, or powerline worker. Photo: Facebook.Source:Supplied

He enjoyed dressing up in medieval garb. Photo: Facebook.Source:Supplied

This photo was possibly taken on Halloween. Photo: Facebook.Source:Supplied

Police found Oppenneer’s decapitated body in a wooded area on Wednesday after receiving a tip off about an abandoned vehicle. The exact cause of his death was unclear.

“We don’t know what trauma was caused because after he was murdered, his head was removed by the suspect,” Wyoming Police Chief James Carmody said on Tuesday.

“We have not been able to locate his head after a very thorough and exhaustive search.”

According to MLive Michigan, police now believe Oppenneer was dead before his head was removed.

Captain Kim Koster said a medical examiner believed Oppenneer died before the body was mutilated but the cause of death has still not been determined.

Investigators said emails indicated that Slocum connected with Oestrike through an ad on the online service Craigslist and arranged a sexual encounter in which Oppenneer would be present.

Police got a warrant to search Oestrike’s home on Thursday night but he fled. Police chased him for a short time until Oestrike crashed his car. He later shot himself in the head.

Another photo of Brady Oestrike with a medieval theme. Photo: Facebook.Source:Supplied

When officers searched his car they found Slocum’s body in the boot.

Investigators collected at least 400 items from Oestrike’s home, described as a “hellish environment”, including firearms, ammunition and knives. They also seized a number of electronics items and possessions from both victims.

Oestrike has a criminal history, including two domestic assault complaints filed by his ex-girlfriend.